You're clearing starting to understand the joint systems in the human body. I would recommend for you to start learning about the proportions of the body as well. By extending your elbow (to its fullest) and measuring with your pencil, you will start quickly recognize spacial and anatomical relationships! For example in most cases the length of the head is equal to that of the foot, ect.
I agree with BD! :) Those looks really amazing, especially for someone who (I assume!) has never drawn with a tablet before.
Besides BD's tip, I have another one for you if you still feel a bit clumsy with the tablet: use it as a regular mouse for when you browse the internet. This greatly helped me when I first started learning how to draw with one. I just used the stylus as a replacement for my mouse and it got me really comfortable with it in a short period of time. :) Hope that helps!